Question: The grades on a chemistry midterm at Santa Rita are normally distributed with $\mu = 81$ and $\sigma = 5.0$. Ashley earned a $79$ on the exam. Find the z-score for Ashley's exam grade. Round to two decimal places.
A z-score is defined as the number of standard deviations a specific point is away from the mean We can calculate the z-score for Ashley's exam grade by subtracting the mean $(\mu)$ from her grade and then dividing by the standard deviation $(\sigma)$ $ { z = \dfrac{x - {\mu}}{{\sigma}}} $ $ { z = \dfrac{79 - {81}}{{5.0}}} $ ${ z \approx -0.40}$ The z-score is $-0.40$. In other words, Ashley's score was $0.40$ standard deviations below the mean.